The snapping or popping of soft connective tissue inside the rear outside aspect of my knee seemed to have a diagonally slanting orientation to it. I could even put my finger tips right on it as it jutted out just below the surface of my skin and feel it suddenly shift or slide almost as a guitar string would. Based on this physical sensation analysis, and after consulting diagrams of the inner anatomy of the knee, I suspected it MIGHT be the popliteus tendon. The surgeon thought it might be be also, but couldn't confirm it. He did confirm, however, that my ACL had been removed, but not my PCL. He did say it could be one of several different tendons or ligaments as the sensation occurred in an anatomically complex area of the knee.